Interfacial properties of a silicone copolymer demulsifier at the air/water interface

Crude oil/water emulsion stability is one of the major obstacles to efficient off-shore separation of undesired aqueous phase. Chemical demulsifiers based on polysiloxanes have been successfully tested as accelerators of phase separation but the mechanism of coalescence is not fully understood. Better understanding of interfacial properties in the presence of demulsifier should give better insight in their mode of action. Comprehensive study of the interfacial properties of small water-soluble PEO-(PDMS)-PEO triblock copolymer is presented in this paper. Insoluble monolayers are formed by deposition of dissolved polymer at the air/water interface but also by adsorption from aqueous solution of the polymer. High affinity of the polymer molecule for the interface i.e. too high the energy needed to remove the molecules from the interface is at the origin of such behaviour. The elastic moduli are function of the surface pressure in the film and are very similar in both Gibbs and Langmuir monolayers.